Tweak the doc of server mode
Tweak the doc of server mode

`TIP:` has a gray background color in antra, so tweak the redundant backticks below.

```consle
You can specify the server host and port with the
$RUBOCOP_SERVER_HOST`and the `$RUBOCOP_SERVER_PORT environment variables.
```

tejasbubane/rubocop,rrosenblum/rubocop,tejasbubane/rubocop,tejasbubane/rubocop,rrosenblum/rubocop,rrosenblum/rubocop